Measurement Of Residual Stresses in Diesel Components using X-ray, Synchrotron, and Neutron Diffraction

by England, Roger D

Abstract (Summary)

The residual stress profile is a major factor on the fatigue life of components that are subjected to cyclic loading.1 The residual stress profiles of two diesel engine components, a section removed from a connecting rod and a section removed from a finished crankshaft, were measured non-destructively using neutron, laboratory x-ray, and synchrotron x-ray diffraction techniques. The synchrotron source identified the near surface residual stresses, and the neutron diffraction technique used for measurements of the residual stresses from 1 mm below the surface on into the interior of the samples. The strains from the synchrotron measurements were corrected for the effect of the exponentially weighted averaging over the irradiated depth using a numerical linear inversion method. The neutron measurements did not require any corrections, as they are a measurement of strains, directly from the area of interest, and they are not weighted. After this determination of the residual stress profiles, the same locations on the components were measured using the common destructive x-ray diffraction etch layer removal technique. The measured data from this iterative etch technique were corrected for the effect of the removed material on the remaining stress field using equations put from the SAE J784a standard.2 These corrected data from this destructive technique is graphed in comparison to the residual stress profile data determined non-destructively. This data proves the etch layer removal method is as accurate as any of the other methods available due to the excellent correlation of the different techniques.